The Lower Palaeozoic Brachiopod and Trilobite Faunas of Anglesey (Part 2 of 2)

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THE LOWER PALAEOZOIC
BRACHIOPOD AND TRILOBITE

FAUNAS OF ANGLESEY

D. E. B. BATES

BULLETIN OF

THE BRITISH MUSEUM (NATURAL HISTORY)

GEOLOGY

Vol. 1 6 No. 4

LONDON: 1968

^^^■^^^^^^^^^■^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^H

^^^^^^^^^^^^^^^^^^^^^^^^^^■^^^^^^^■^^^^^^■^H

AND TRILOBITES OF ANGLESEY 181

corners. Glabella clavate, reaching to the anterior border, evenly convex (sag.
and tr.)' f narrowest just behind the midline (sag.), just longer than wide; without
glabellar furrows. Axial furrows convex inwards, well defined. Occipital ring
not seen. Fixigenae incomplete, evenly convex (long.), palpebral lobe and course
of facial suture not seen. Anterior border not separated from glabella mesially,
but present in front of the fixigenae; anterior border furrow well defined, meeting
the axial furrow in a right angle, and continuing a little way adaxially to define the
anterolateral corner of the glabella. Ornament of coarse terrace lines, averaging
five to eight per 5 mm., becoming crowded together on the anterior border, trans-
verse across the glabella, borders and anterior part of the fixigenae, not preserved
elsewhere.

Librigena incomplete, triangular, convex (long.), with prominent anterolateral
border furrow, no posterior border furrows. Eye lobe large, semicircular. Genal
spine long, circular in cross-section. Ornament of distant terrace lines, diverging
on either side of eye.

Type specimens (measurements in mm.)

Length Width

Holotype. Incomplete cranidium (In. 58291) . . 28*8 —

Paratypes. Incomplete cranidium (In . 58292) . — —

Internal mould and interior of incomplete
librigena (In . 58293a-b) ... — —

Type horizon and locality. Garn Formation, limestone blocks in breccia
beds, Porth Padrig, Mynachdy. N.G.R. 30539279.

Discussion. Protobronteus was erected by Snajdr (i960 : 245-246) to include
only Eobronteus reedi Sinclair (1949 : 51-52). In this species, as in P. greenlyi
the glabella is clavate, without any glabellar furrows, and coalesces with the anterior
border. E. curtus Sinclair (1949 : 50-51) is very similar and could well be included
in Protobronteus as the glabellar furrows are indistinct and the anterior border
furrow fades out mesially.

P. greenlyi differs from both these species in that the inner anterior border furrow
is absent (the cheek furrow of Sinclair 1949 : 51), and the ornament is differently
developed. In P. reedi the terrace lines are longitudinal between the two border
furrows, and in E. curtus they are not developed in the same place, only coarse
punctae being present.

Family ILLAENIDAE Hawle & Corda 1847

Subfamily ILLAENINAE Hawle & Corda 1847

Genus ILLAENUS Dalman 1827

Illaenus sp.

(PL 12, figs. 8-13, 15)

1919 Illaenus caecus Holm (partim); Lake in Greenly : 478.

Description. Cranidium quadrangular, evenly convex (tr.), longitudinal con-
vexity strong posteriorly, weak anteriorly. Glabella short and wide, with slight

i82 LOWER PALAEOZOIC BRACHIOPODS

independent convexity (tr,) $ two-thirds the width of the cranidium. Axial furrows
curve inwards for two-thirds of their length, and end in an outwards curve. Pal-
pebral lobes one-third the length of the cranidium, situated less than their own
length from the posterior margin. Posterior branches of the facial sutures short,
running directly backwards, anterior branches slightly divergent. Dorsal surface
of cranidium smooth,

Pygidium parabolic, the anterior margin slightly convex forwards, width four-
thirds the length, convex, the inner pleural fields gently convex and the margins
deflected at about 45 °. Axis short, sub- triangular, with independent convexity
(tr.), four-tenths the width of the pygidium. Axial furrows shallow posteriorly,
meeting at about 6o°, Short (long.) articulating half ring. Pleural fields with
anterior borders slightly swollen, marked off by shallow depressions. Articulating
facets sharply bevelled, with terrace lines extending beyond them. Rest of dorsal
surface finely pitted. Doublure close to the dorsal shield, convex ventrally at its
outer margin, almost half the length (sag.) and one-tenth the width of pygidium at
anterior margin. Inner margin commencing near midline of facet (tr.), swinging
in a curve gradually decreasing in radius to the midline of the pygidium, where a
forward pointing cusp is found, Ventrally deflected median ridge strongly marked.
Doublure bears terrace lines running parallel to its margins about 07 mm. apart.

Figured specimens (measurements in mm.)

Length Width

Cranidium (In. 58294) . ♦ . . . — 9-9

Pygidium (In . 58295) . - . * . 23-7 32-7

Pygidium (In , 58296) . . . . . 22-6 33 * 5

Discussion. The species resembles Illaenus revaliensis (Holm 1886 : 87-92,
pi- 2, figs. 1-10) particularly in the shape and other features of the pygidium. The
axis is similar, and the inner margin of the doublure has a forward pointing cusp at
the midline. The cranidium is poorly preserved, and may possibly be a crushed
and distorted cranidium of Stenopareia ci linnarssoni (Holm), but the glabella is
relatively wider, the palpebral lobes are much larger, and the anterior margin seems
to be sharply truncated.

Genus STENOPAREIA Holm 1886
Stenopareia cf. linnarssoni (Holm)

(PL 12, figs. 14, 16-23)

1919 Illaenus caecus Holm (partim); Lake in Greenly : 478)

Description. Cranidium quadrangular, the frontal area domed, strongly and
evenly convex (long, and tr.). Glabella with slight independent convexity (tr.),
half the length of cranidium. Two pairs of oval muscle scars between the axial
furrows, the anterior pair indistinct, Axial furrows poorly defined on dorsal, but
well defined on ventral surface, extending forwards half the length of cranidium,
widening in their anterior half to be well defined on the ventral surface. Palpebral
lobes less than one fifth the length of cranidium, less than their own length from

AND TRILOBITES OF ANGLESEY 183

the posterior border. Posterior oraches of facial suture short, straight, running
diagonally outwards, anterior branches straight, converging slightly forwards.
Glabella and fixigenae with smooth dorsal surfaces, frontal margin with faint terrace
lines on the ventral surface.

Librigena twice as long as wide, tapering to a point anteriorly, with vertically
deflected border present anteriorly. Genal angle very broadly rounded.

Rostral plate triangular, anterior margin gently convex outwards, the posterior
margins concave rearwards, meeting in a central cusp with an angle of less than go .
Ventral surface with terrace lines.

Pygidium semi-oval, just over half as long as wide, weakly convex except at the
sides where almost vertically deflected. Axis one-third the anterior width, un-
defined posteriorly, evenly convex (tr.). Axial furrows shallow, only seen at anterior
margin. Dorsal surface smooth. Articulating facets convex, almost vertical.
Doublure lies close to the dorsal surface, with a faint median ridge, anterior margin
monocuspid(P).

Figured specimens (measurements in mm.)

Cranidium (In. 58297)
Cranidium (In. 58298)
Librigena (In. 58299) .
Rostral plate (In. 58300)
Pygidium (In. 58301) .
Pygidium (In. 58302) .

Horizon and locality. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.

Discussion. The cranidium is very similar to that of Stenopareia linnarssoni
(Illaenus linnarssoni Holm in Warburg 1925 : 1 15-123, pi. 2, figs. 14-18). The
glabellar proportions and the axial furrows are the same, with an anterior swelling
of the furrows. The palpebral lobes are the same size and equally far back. The
pygidia are approximately similar in proportion; the inner margin of the doublure
is unknown, though it also has a ventrally deflected median furrow. The facets
are narrow and rounded in both cases, but the axis is relatively narrower in the
Anglesey specimens. Stenopareia camladica Whittard (1961 : 216-217, pi- 3°> n g s -
10-13) nas a similar cranidium, but the axial furrows are poorly preserved, and the
pygidium is differently proportioned in the Shropshire species.

Family HARPIDAE Hawle & Corda 1847

Genus SELENOHARPES Whittington 1950

Selenoharpes (?) sp.

(PI. 13, figs. 1-2, 5-6)

Description. Outline of cephalon oval; greatest width probably behind the
occipital ring.

Glabella tapering forwards, width at its base seven-ninths of its length, rounded

Length

Width

15-5

18-6

14-6 (est.)

19-7

8-9

22-6

23'4

42-4 (est.)

13-5

22-5

i8 4 LOWER PALAEOZOIC BRACHIOPODS

anteriorly; sharply convex and carinate, in height equal to its width; in lateral
profile becoming vertical anteriorly. Basal lobes triangular, very vague, one-third
the length of the glabella, marked by shallow furrows running inwards and back-
wards. Axial, preglahellar, and occipital furrows all shallow. Occipital ring one-
ninth length of the glabella, bent up with it,

Pre-glabellar field one-third length of the glabella, sloping anteriorly. Eye
tubercles prominent and elevated above the cheeks, opposite the anterior one-
fifth of the glabella. Eye ridges broad, running directly inwards. Genal ridges
fine, running outwards and backwards to the girder. Alae one-third the length
of the glabella, depressed, marked by semicircular alar furrows. Cheek lobes bent
down ant erolater ally and laterally. Posterior border with sharply raised convex
rim, continuous with a similar rim on the inward side of the prolongations. Cheek
roll not separable from the cheeks. Brim equal in width anteriorly to the glabellar
length, convave, with a row of prominent pits just inside the rim marking the
inner edge of a downward bevel round the rim. Girder smooth, with prominent
pits forming a single row on both sides ; girder possibly meeting the internal prolonga-
tions. Glabella and alae smooth; preglabellar field and cheek lobes anterior and
lateral to the eyes with radiating ridges with fine pits between them; on the rest
of the cheeks and on the brim are similar fine pits but without ridges or arrangement,

Figured specimen. Incomplete cranidium (In. 58303).

Horizon and locality. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R, 30539279.

Discussion. The two closest genera are Selenoharpes and Aristokarpes t the
former of Middle Ordovician (post-Llandeilo) age and the latter of Llandovery age.
In Selenoharpes the glabella tapers forwards, the eye ridges are prominent and genal
ridges are present. In Aristokarpes the glabella is sub-parallel sided, eye ridges
are weak and genal ridges absent. It also has much smaller alae than Selenoharpes,
which are one-quarter the length of the glabella compared with one-half. There is
thus some doubt as to where to place these specimens, which compare closely with
Selenoharpes, except for the smaller alae, a difference that is probably trivial. The
specimens are certainly not conspecific with the type species, S, youngi (Reed)
from the lower Caradoc of Girvan, in which the brim is convex upwards.

Family TRINUCLEIDAE Hawle & Corda 1847

Subfamily CRYPTOLITHINAE Angelin 1854

Genus BERG AMI A Whittard 1955

Bergamia (?) sp.

(PL 13, figs. 3^4, 9, 13)

Description, Cephalon twice as broad as long, Glabella pyriform, swollen,
tapering markedly posteriorly, second and third furrows fairly well marked, pit-
like in form ; well marked alae bounded laterally by deep furrows, ending laterally
against the posterior border in well marked knobs ; glabellar furrows not well marked

AND TRILOBITES OF ANGLESEY 185

against the alae, Genae swollen, crossed by a ridge running obliquely back from
the front of the glabella to the genal angle. Occipital ring very narrow, arched
and convex posteriorly; posterior borders from a narrow sharp ridge posterior to
a wide shallow furrow. Glabella and genae posterior to the ridge bear a strong
reticulate pattern, becoming faint towards the front of the glabella. Fringe of
uniform width throughout except at the genal angle ; pits sunk in deep radial sulci ;
girder not seen in any of the specimens; sulci number eighteen on each side of the
centre-line, with up to four pits in each; interradial sulci numbers i and ii present;
some twin pits.

Thoracic segments not well preserved; axis strongly convex with axial rings
convex posteriorly; pleural regions with strong oblique pleural furrows; pleural
spines strong and directed posteriorly-

Pygidium over twice as wide as long, triangular in outline; axis tapers at 30
with at least five axial rings, well defined and strongly arched; pleural lobes divided
by at least four faintly marked oblique interpleural furrows; anterolateral angles
bevelled as an articulating facet; posterior margins with a broad border of uniform
width, slightly raised over the centre-line*

Figured specimens. Counterpart moulds of cranidium and pygidium (In.
5830421-13). Length of cranidium (sag.) 3*4 mm., width 7-0 mm. Length of pygi-
dium 17 mm., width 4*2 mm.

Counterpart moulds of complete dorsal carapace (In.g8305a-b), Length (sag.)
2 -5 mm.

Ventral mould of dorsal carapace (In. 58306) Distorted.

Horizon and locality. Shales, D. hifidus zone, quarry 100 yds. north of
Gwredog-uchaf farm, Rhodogeidio. N.G.R. 40488628,

Discussion. The preservation of the specimens, in particular of the fringe, is
not good enough to make a certain generic identification, However, the simplicity
of the fringe suggests that the specimens belong to Bergamia, which ranges from
the uppermost Arenig through the Llanvirn, and possibly into the Caradoc (Whittard
1955 : 31). The species resembles B* rhodesi Whittard (1955 : 32) in the arrange-
ment of the pits on the fringe. The smallest specimen illustrated (PL 13, fig. 3)
is a meraspid of probably degree two. There is little difference in characters from
the larger specimens.

Family RAPHIOPHORIDAE Angelin 1854

Genus AMPYX Dalman 1827

Ampyx sp. (1)

(PL 13, % 8)

1 919 Ampyx el domains (Angelin); Lake in Greenly : 446.
1955 Ampyx sp.; Whittard : 17.

Figured specimen. Cranidium (Af .824). Length 9-0 mm., width 12*4 mm

i86 LOWER PALAEOZOIC BRACHIOPODS

Horizon and locality. Carmel Formation, sandstones on the escarpment 300
yds. west of Bryn Gollen Uchaf. N.G.R, 4055 83 80 .

Discussion. This specimen remains the only one collected from the basal grits,
and there is nothing that can be added to Whittard's opinion that it probably
belongs to an undescribed species,

Atnpyx sp. (2)

{PL 13, figs. 7, 10-12)

191 9 Ampyx nasuttis Dalman; Lake in Greenly : 433.

Description, Cranidium quadrilateral in outline, length four-tenths the width,
the anterior border very well developed. Glabella pyriform, widest near the
anterior end and broadly rounded in front, one-third to one-quarter the width of
the cranidium in front, tapering to the occipital ring, exceptionally weakly swollen,
overhanging only part of the preglabeUar field. One pair of glabellar furrows
almost isolating long narrow lobes, the furrows running back parallel to the axial
furrows, starting just anterior to the transverse midline of the glabella; alae (cf.
Whittard 1955 : 15) erescentic, starting anterior to the glabellar furrows and
extending backwards to meet the posterior border furrow, axial and alar furrows
faint; glabellar spine at least half as long as the cephalon, circular in cross section,
possibly concave dorsally. Fixigenae triangular, gently convex. Facial suture
runs in a gentle sigmoidal curve convex outwards as it crosses the posterior border,
convex inwards forwards of this and again convex outwards in its anterior third.
Occipital ring narrow, occipital furrow shallow, both convex backwards- Posterior
border furrow broad and shallow, running obliquely outwards and backwards,
but sweeping forwards again near the genal angle; posterior border widening laterally.
Pre-glabellar field comparatively long, about one-sixth the length of the cephalon,
flattened.

Thorax of six segments, broad and flat. Axis convex, axial rings each with a
shallow groove defining small lobes at each side. Pleurae parallel-sided, each
with an oblique furrow curved forward at the tip, sharply deflected vent rally at
prominent fulcral processes which appear as tubercles. First or macro-pleurae
longer than the others with outer margins not deflected but sloping backwards and
out to the fulcrum. Other pleurae with blunt terminations,

Pygidium triangular, twice as wide as long. Anterior margin straight, postero-
lateral borders slightly convex, deflected, with terrace lines parallel to the margins.
Axis convex, with narrow articulating half-ring, tapering from one-fifth the width
of the pygidium anteriorly to a point at the posterior end, occasionally a few axial
rings present. Pleural lobes smooth, except for strongly developed anterior borders,
marked off by sharp furrows running obliquely backwards and outwards, becoming
concave forwards laterally to meet the anterolateral angle of the pygidium. Pro-
minent fulcral tubercle at the inner end of the articulating facet .

AND TRILOBITES OF ANGLESEY 187

Figured specimens {measurements in mm.)

Length Width

Internal and external moulds of cranidium (In.

58307a-b) 16 -o 35-6 (est.)

External mould of cranidium (In . 58308) . — —

Internal mould of thoracic segments and pygidium

(Af.3653) 16-3 I9'3

External mould of pygidium (In . 58309) . . 7-0 16 • 8 (est.)

Horizon and locality. Tandinas shales, by the track leading down to the
quarry, and on the shore behind the power house, at Tandinas quarry, Careg-onen.
N.G.R. 58248187.

Discussion. The species is similar to A . linieyensis Whittard of the Shelve area
(D. bifidus zone), but differs in having a short, weakly swollen glabella, a pre-glabellar
field, and having terrace lines on the pygidium. A. salteri Hicks (D. extensus
zone?) also has terrace lines to the pygidium, but lacks a pre-glabellar field.

Family CHEIRURIDAE Salter 1864

Subfamily GHEIRURINAE Salter 1864

Genus CERAURINELLA Cooper 1953

Ceraurinella sp.
(PL 13, figs. 14-22)

Description. Cranidium roughly triangular in outline, broader than long.
Glabella evenly convex (tr.), gently convex (sag.) becoming more convex along
the anterior lobe. Length equal to the maximum width, the latter across the
anterior lobe, sides slightly tapering towards the occipital ring, front margin convex
forwards. Three pairs of narrow well marked glabellar furrows; ip inclined ob-
liquely backwards, bent back to join the occipital furrow nearer the midline than
the axial furrows; 2p and 3p parallel to each other, curving obliquely backwards
and crossing one-third the width of the glabella (tr.). Basal lobes with independent
convexity, one and a half times the length (exsag.) of the second and third lobes;
the latter subequal in length without independent convexity. Occipital furrow-
not well seen, shallow. Fixigenae triangular convex, eye lobe on the highest part,
opposite and close to the second glabellar lobe, equal in length to that lobe (exsag.).
Anterior part of fixigenae parallel sided, anterior branch of facial suture running
in to meet the axial furrows just in front of 3p glabellar furrows. Posterior branch
of facial suture runs transversely out from the eye, and curves round to meet the
anterolateral border of the cranidium. Posterior border furrows deep and wide,
bending sharply forwards to meet the lateral border furrow. Posterior border
widening laterally towards genal spine, length of latter unknown. Glabella and
borders smooth, fixigenae coarsely tuberculate. Librigenae unknown.

Hypostome slightly longer (sag.) than maximum width (tr.) across anterior wings,

igg LOWER PALAEOZOIC HRACHIOPODS

tapering backwards to a width at the posterior border half the maximum. Median
body convex (sag. and tr.) widest in front of anterior wings. Anterior, lateral and
posterior border furrows broad and shallow. Middle furrows faint, running in
from opposite shoulders to end in shallow pits. Posterior lobe crescentic, independ-
ently convex where marked off by the middle furrows. No anterior border medianly.
Anterior wing slopes steeply dorsoposteriorly, tip narrow and spine-like. Lateral
border commences opposite anterior wing, widens rapidly to prominent and sharp
shoulder (in ventral view) wlrch is just less than half the way back (exsag) from
the anterior border, continuous with the posterior border. Short denticle or spine
on the posterolateral corners, posterior border straight. Posterior wing not seen.
Entire surface smooth.

Thorax of unknown number of segments. Axis arched, most sharply convex
over the midline, length [sag) one-fifth the width, width one-quarter that of the
whole segment. Anterior margin convex forwards over the midline, concave
forwards laterally above the apodemes, which are deflected vent rally (no articulating
half -ring seen). Inner part of pleura horizontal, divided in two by a furrow parallel
to the axial furrow, the inner part being one-third the width of the whole, and
crossed by a diagonal furrow, the outer part bent abruptly ventrally and forming
a gradually tapering pleural spine. No ornament on the segments.

Pygidium poorly preserved. Convex axis with four axial rings, or three axial
rings and an articulating half ring. Margin not preserved, except for one long
tapering spine probably commencing opposite the second axial ring and curving
backwards towards its tip, No ornament present.

Figured specimens (measurements in mm.)

Incomplete glabella (In. 58310)
Incomplete glabella (In.58311)
Incomplete cranidium (In. 58312)
Hypostome (In. 58313)
Hypostome (1^583x4)
Hypostome (In. 58315)
Thoracic segment (In. 58316)
Thoracic segment (In. 58317)
Incomplete pygidium (In. 58318) -

Horizon and locality. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279,

Discussion. The specimens are assigned to Ceraurinella since the eyes are
opposite the 2p lobes and near the glabella, the genal spines though not complete
are short, the pygidium has the long spines typical of that genus (and Ceraurus),
and the thoracic segments and hypostome also are of the same type. The species
described by Cooper (1953 : 29-30) and by Whittington & Evitt (1953 : 62-70)
differ in their ornament, which is more pervasive, and possibly also in other minor
details. None of the species of Ceraurus (Raymond & Barton 1913; Barton 1913)

Length

Width

8-7

— ■

10-3

13*6

7-9

5'4

9.1

AND TRILOBITES OF ANGLESEY 189

corresponds, Ceraurinella? sp. has been recorded by Whit ting ton from the D erf el
limestone (in Whittington & Williams 1955 : 422-423, pi. 40, figs. 102, 107 and
in), but the two species are not the same, as in his figures the eyes, not preserved,
cannot have been farther back than opposite the 3p glabellar lobes, and the 3p lobes
seem to be longer (sag.) than the others.

Subfamily SPHAEREXOCHINAE Opik 1937
Genus SPHAEREXOCHUS Beyrich 1845

Sphaerexochus sp.

(PL 14, figs. 1^2)

Description. Cranidium only preserved, distorted by flattening, crescent shaped
in outline, original convexity not known. Glabella subcircular to pentagonal in
outline, widest opposite the second glabellar furrow (2p). Occipital ring narrower
than the glabella at its maximum, one-eighth of glabella length (sag), convex,
posterior margin concave backwards, Occipital furrow broad and deep, uniformly
curved throughout. First glabellar furrows (ip) transverse with a gently concave
backwards curve, curving sharply at their inward ends towards the occipital furrow,
running to meet it in another gentle curve convex sagit tally. The first lateral
glabellar lobes isolated, subquadrate in outline, possibly without independent con-
vexity, four-ninths the length of the glabella (sag.), approximately two-ninths its
width. Second glabellar furrow (preserved only on one side) very short, straight.
Second glabellar lobe one-half length of the first. No third glabellar lobes or furrows.
Anterior border not preserved, Fixigenae small, triangular, convex. Palpebral
lobe very narrow, opposite to ip furrow, two-thirds the length of the first lobes.
Facial suture not seen forward of the eye. Posterior branch runs outwards and
then backwards to meet the posterior border at right angles. Posterior border
equal in width to the occipital ring at its inner end, widening towards the genal
angle. Posterior border furrow concave forwards, dying out towards the genal
angle.

Figured specimen (measurements in mm.)

Length Width

Cranidium (In. 58319) . « . . 6*0 (sag.) 9*5

Horizon and locality, Tandinas shales, on the shore by the powerhouse,
100 yds. west of the pier, Careg-onen, N.G.R. 58208193.

Discussion. The specimen differs from all described species of Sphaerexochus
by having two pairs of lateral glabellar furrows. S. hilobatus {Whit tar d 1958 : no)
has only the basal pair developed, otherwise three pairs seem to be the rule. The
preservation of the specimen has resulted in accentuation of the anterior furrow
on one side, and its obliteration on the other. It is possible, though unlikely that
a third pair of furrows may be present, but obliterated.

geol. 16, 4. ig

igo LOWER PALAEOZOIC BRACHIOPODS

Family PLIOMERIDAE Raymond 1913

Subfamily PLIOMERINAE Raymond 1913

Genus PLIOMEROPS Raymond 1905

Pliotnerops sp.

(PL 14, figs. 3-4, 6-7)

Description, Cranidium incomplete. Glabella quadrangular, expanding for-
wards from the occipital ring to midway between the pre-occipital and middle
furrows, forwards of this having a domed margin, slightly flattened in the centre.
Dorsal furrows deeply impressed. Pre-occipital furrows (ip) commencing at one-
third the length of the glabella forwards from the occipital ring, running obliquely
inwards and backwards for one-quarter the width of the glabella, at that point
turning abruptly to run slightly forwards, finally curving round to point obliquely
backwards at their inner tips, which are separated by one-eighth the width of the
glabella, Middle furrows (2p) commencing just forwards of two- thirds the length
of the glabella, running inwards and backwards to as near the midline as the pre-
occipital furrows, the tips of the inner ends of the two pairs of furrows being much
closer together than their outer ends. Anterior furrows (3p) located on the anterior
margin, half way between the midline and the anterolateral corner of the glabella,
faint and short, being little more than indentations of the margin. Rear two pairs
of glabellar lobes with independent convexity. Axial furrows of the same depth
as the glabellar furrows, curving smoothly into the anterior border furrow. Occipital
furrow convex forwards at centre, becoming concave forwards towards the axial
furrows. Occipital ring not completely preserved, lengthening (sag.) towards the
midline. Anterior border strongly arched dor sally over the midline, widest at the
midline and at the anterolateral angles of the cephalon. Fixigenae incompletely

Hypos tome shield-shaped, anterior border convex, lateral and posterior borders
with a sigmoidal curve ending in a posterior point, slightly wider than long, almost
flat. Middle body of same shape. Anterior lobe produced into lateral wings,
posterior lobe crescentic, defined by middle furrows commencing just behind the
wings, broad and shallow, curving gradually inwards. Anterior border poorly
preserved, widest at the anterior wings. Lateral and posterior borders of uniform
width except at their anterior ends. All border furrows wide and shallow.

Pygidium with shape of an extremely taut bow, just longer than wide, anterior
margin very convex forwards. Convex {if), the margins deflected ventrally at
angles up to 90 , almost flat (sag.), but convex (exsag.). Axis convex, of five fiat-
topped (sag.) axial rings, tapering backwards, followed by a terminal axial piece
one and one half times as long as the rings, parallel sided for half its length and
tapering to a point in the posterior half. Pleural portions of five pleural lobes,
without a border, each lobe widening to the margin and truncated to produce a
smooth lateral and posterior border ; the last pair surrounding the axis and separated
by a median furrow.

AND TRILOBITES OF ANGLESEY 191

Figured specimens (measurements in mm.)

Length Width

Incomplete cranidium (In . 58320) . . . 16-5 —

Hypostome (In . 58321) . . . . . 14-5 —

Pygidium (In. 58322) . . . . . .39-0 —

Internal mould and interior of pygidium (In.

58323a-b) — 17-0 (est.)

Horizon and locality. Gam Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.

Discussion. The above descriptions are of isolated pieces from the limestone
blocks, and, assuming they belong together, they are assigned to the genus Pliomerops
Raymond on the basis of the diagnosis given by Harrington (in Moore 1959 : 440).
The anterior border is not denticulate, there is no median indentation of the glabella,
and the terminal axial piece is long and enclosed. The cranidium resembles that
of P. canadensis (Billings) illustrated in the Treatise (Moore 1959 ; fig. 345, 2b)
but the pygidia do not. As far as can be seen, most of the described species of
Pliomerops have short terminal axial pieces and usually a denticulate margin,
though the diagnosis in the Treatise (Moore 1959 : 440) states that the terminal
axial piece is long. Reed (1906 : 153, Plate XIX, fig. 16) figures a pygidium very
like this as Pliomera sp.

B. N. Cooper (1953) has described a pliomerid from Virginia, Pliomerella ameri-
cana, which is somewhat similar to the Anglesey specimens. The pygidium appears
to be identical, to judge from PI. 10, fig. 4 of his paper. This is a crushed specimen,
but the long axial piece is apparently enveloped by the posterior pleurae. Another
pygidium is illustrated in fig. 1 of the same plate, in which the terminal axial piece
is quadrate and reaches the posterior margin, though it may be that the posterior
part is missing, and the caption states that the specimen is incomplete. Cooper's
text does not indicate whether the axial piece is enveloped or not, and the specimen
of his PI. 10, fig. 1 is re-illustrated on p. 445 of the Treatise (Moore 1959 : fig.
348, 2b) as being in fact complete. The accompanying text in the Treatise (Moore
1959 : O445) states that a pygidium of this sort is diagnostic of Pliomerella. The
genus was erected by Reed (1941 : 269) for trilobites with two pairs of glabellar
furrows 'combined with some characters of Pliomera', but he did not describe a
pygidium. It is thus probable that Pliomerella americana Cooper does not belong
to Pliomerella, but possibly to Pliomerops, though there is no sign in Cooper's figures
of the anterior glabellar furrows, nor does he describe them in the text.

Subfamily PLACOPARIINAE Hupe 1953
Genus PLACOPARIA Hawle & Cor da 1847

Placoparia sp.
(PI. 14, fig. 5)

1919 Placoparia sp.: Lake in Greenly : 466*

Figured specimen. Dorsal carapace (Af.1319}. Length 23*1 mm,

GEOL. 1 6, 4. I9§

T g2 LOWER PALAEOZOIC BRACHIOPODS

Horizon and locality. Shales of the GL teretiusculus zone, 80 yds, north of
the streamlet, on the shore at Porth-y-gwichiaid (Greenly 1919 ; 466), N.G.R.
48799160,

Discussion. The species P. zippei (Boeck) has recently been divided into two
species, P. zippei and P. harrandei Prantl & Snajdr, differing in a number of small
features, including the glabellar shape, details of the glabellar and occular furrows,
and the development of vincular notches (Whittard 1966 : 283-284). P. harrandei
itself is a synonym of P. cambriensis Hicks (1875 : 186, pi. 9, figs, 1-2) (Dr. W, 1\
Dean, personal communication) .

The Anglesey specimen belongs more probably to P. cambriensis, as the glabella
is quadrate rather than trapezoidal in outline, though the evidence of the other
features is equivocal, probably due to crushing of the specimen.

Family CALYMENIDAE Burmeister 1843
Subfamily CALYMENINAE Burmeister 1843

Calymenid undet.
(PL 14, figs. 8-9, 12-13)
Figured specimens (measurements in mm.)

Length

Width

6-7

5*6

9-3

n-5

Hypostome (In. 58324) .....

Pygidium (In. 58325) .,...*

Horizon and locality. Garn Formation, limestone blocks in breccia bed,
Forth Padrig, Mynachdy. N.G.R, 30539279.

Discussion. The material found consists of one complete pygidium, and one
complete and one incomplete hypostome. It is assumed that they all belong to
one species.

The pygidium is oval in outline, and strongly convex. The axis gradually tapers
backwards, not reaching the posterior border, with six well defined axial rings,
a terminal piece and an articulating half ring. The pleural portions show deep
pleural furrows with much shallower interpleural furrows, extending to the margin
but becoming much fainter on the border. The border is marked by faint depres-
sions running from the tip of the axis to the anterior margins. There are well
defined and almost vertically deflected articulating facets, with the foremost pleural
groove extending onto them. In posterior view the lateral and posterior margins
show a strongly marked arch across the midline. The entire surface, except for
the articulating facets and the furrows, is finely tuberculate.

The hypostome is longer than wide, rectangular in outline. The middle body
is parallel-sided, with faint diagonal middle furrows dividing off a crescentic posterior
lobe, convex longitudinally and sharply convex transversely, without a raised
central portion to the anterior lobe. The anterior border is flexed vent rally, con-
tinuous with large anterior wings. The lateral borders have a wide gently curved
notch extending from the anterior wings to opposite the anterior end of the posterior
lobe. The lateral and posterior borders behind this are wide and flat, produced

AND TRILOBITES OF ANGLESEY 193

into points almost one- third of the length of the hypostome, separated by a deep
median notch extending to the end of the middle body. The tips of the points
and the notch are all sharp, each with an angle of about 50 .

Subdivision of the Calymeninae is based mainly on cephalic characters, so it is
not possible to give a generic designation. The upper Ordovician calymenid species
have been assigned to five different genera by Shirley (1936 : 400), and of these
Platy calymene, Gravicalymene and Flexicalymene agree in their pygidal characters.
Flexicalymene is the closest in character, and the pygidium described and figured
by Shirley (1936 : 406, pi. 29, fig. 7) looks similar, though it is more angular in
outline.

Family HOMALONOTIDAE Chapman 1890

Subfamily EOHOMALONOTINAE Hupe 1953

Genus NESEURETUS Hicks 1872

Neseuretus monensis (Shirley)

(PL 14, figs, ir, 16)

iqiq Calymene parvifrons Salter; Lake in Greenly : 442, 446,
igig Calymene tristani Brongniart; Lake in Greenly : 442.
1936 Synhomalonottis monensis Shirley : 401.

Figured specimens (measurements in mm,)

Length Width

Internal and external moulds of pygidium (In.
58326a-b) . . . . . . . 16-9 21-0 (est.)

Internal mould of pygidium (In. 58327) . * distorted

Horizon and locality, Carmel Formation, sandstones; In,58326a-b from 440
yds. north of Ty-hen, Treiorwerth, N.G.R. 35767891; In. 58327 from 120 yds.
north-west of Chwaen-bach, Llanerchymedd, N.G.R. 39468378,

Discussion, Shirley described this species from specimens in Greenly 's collection
(G.S.M, Af. 930-2), The thorax, librigenae and pygidium were not represented
in the collection, so only the cranidium was described. Pygidia have been found
from the same horizon, and give additional information on the species. The speci-
men from Chwaen-bach is distorted, and the description is based on that from
near Ty-hen (In . 58326) .

The pygidium is broader than long, roughly elliptical but with the anterior margin
more strongly curved than the borders. The axis bears an articulating half ring
and furrow. The axis is funnel-shaped, the tapering portion containing at least
six rings, followed by an almost cylindrical portion terminating in a rounded end
not quite reaching the posterior margin. The pleural lobes are gently convex, and
bear six rounded unfurrowed pleurae, separated by well marked interpleural furrows.
The border is sharply rounded, but the form of the doublure is unknown. The
pygidium from Chwaen-bach shows pleural furrows which may be the result of
crushing.

194 LOWER PALAEOZOIC BRACHIOPODS

Family LICHIDAE Hawie & Corda 1847

Subfamily TETRALICHINAE Phleger 1936

Genus AMPHILICHAS Raymond 1905

Amphilichas sp, (x)

(PL 14, figs. 10, 14-15, 17)

Description. Cranidium roughly pentagonal, strongly bent down at the an-
terior and posterior lateral corners. Glabella rounded, axe-shaped, as broad as
long, strongly convex, overhanging in front. Front ero-median lobe prominent,
expanded in front to more than twice its basal width; anteriorly strongly convex;
anterior lateral angles rounded; posteriorly parallel sided and less convex. First
lateral (longitudinal) furrows run inwards towards centre of lobe, curving steadily
round to become parallel and meet the occipital furrow at right angles. Lateral
lobes gently convex, a little less elevated than the median lobe; bluntly pointed
in front, strongly bent down with the antero-median lobe; posterolateral angles
extend considerably further back than the median lobe. Axial furrows as strong
as longitudinal furrows, posteriorly parallel to them, diverging slightly in front of
the eyes. Occipital furrow straight and horizontal behind median lobe, directed
obliquely backwards behind the lateral lobes, and less obliquely behind the fixigenae.
Occipital ring not completely preserved but possibly widest behind the median
lobe. Fixigenae posteriorly equal in width to the lateral lobes, narrowing to less
than half that width opposite the eye; expanding in front of the eye; expanding
in front of the eye but not completely preserved. Course of facial suture only
seen round eye, running outwards behind it. Palpebral lobe semicircular, convex
inwards; its length is one-fifth that of the glabella and its posterior end level with
the occipital furrow. Entire cranidium, except for the furrows, covered with
tubercles of varying size, irregularly placed.

Hypostome oval in outline, broader than long. Posterior border broad, posterior
margin indented. Middle body circumscribed. Posterior lateral lobes well defined
by median furrows running inwards slightly posteriorly with short bifurcations
at their inner ends. Lateral borders broad, with short triangular wings opposite
the posterior border furrow. Anterior border appears to be lacking. Anterior
part of middle body pitted; anastomosing ridges or terrace lines on remainder of
surface.

Figured specimens (measurements in mm,)

Length Width

Incomplete cranidium (In . 58328) . . . 14*9 —

Hypostome (In . 58329) . ( „ . 5*8 (sag.) 7 * 9

Horizon and locality. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.

Discussion. No thoracic segments have been found, and the only remains of
pygidia so far found are too incomplete to describe; they only show the typical
development of tubercles, The cranidium shows similarities to A, wahlenbergi

AND TRILOBITES OF ANGLESEY 195

Warburg from the Leptaena Limestone in Dalarne, and also to Lickas (Ampkilichas)
hibernicus (Portlock) (Reed 1906 : 106, pi. 15, ft. 1 non 2-3).

Amphilichas sp. (2)
(PI. 14, figs. 18-19)

Description. Outline possibly semicircular, weakly convex both longitudinally
and transversely, probably crushed. Frontero-median lobe convex, expanding
forwards to over twice its posterior width; the longitudinal furrows being parallel
posteriorly and curving outwards to diverge at more than 90 where they meet the
axial furrow, not reaching the occipital furrow but ending in a pit. Tricomposite
lobe widening very slightly forwards, at its posterior end the same width as the
median lobe posteriorly; axial furrows concentric with the longitudinal furrows
but with smaller radius of curvature. Fixigena incomplete, narrow, posterior to
the eye less than half the width of the tricomposite lobe, cut into by the eye lobe,
which is one-fifth the length of the cranidium. Only a fragment of the occipital
ring preserved. Surface evenly pitted.

Figured specimen (measurements in mm.)

Length Width

Incomplete external mould of cranidium (Af.
3000) ....... 17 app. —

Horizon and locality. Tandinas shales, by the track 50 yds. west of Tandinas
quarry, Careg-onen. N.G.R. 58248187.

Discussion. There appear to be no basal lobes, so that the specimen belongs
to Amphilichas, although there is little to compare closely with Amphilichas sp. (1)
from Porth Padrig.

Family uncertain

Genus MONELLA nov.

Diagnosis. Genus similar to Glossopleura Poulsen, but differing in having more
strongly marked glabellar furrows, the anterior ends of the palpebral lobes not
touching the glabella, and eleven (compared with eight) thoracic segments.

Type species. Monella perplexa sp. nov. from the Carmel Formation.

Discussion. The specimens assigned to the new genus were referred by Lake
(in Greenly 1919) to Ogygia, but certainly do not belong to the suborder Asaphina,
The thorax consists of eleven segments and the glabella is distinctly furrowed,
a combination of characters that is quite different from any contemporary trilobites,
but generally characteristic of the Order Corynexochida, though the rostral plate
and hypostome have yet to be found. The glabella is clavate and reaches the
anterior margin, the eyes are large and semicircular, with prominent palpebral
lobes, though eye ridges are not present. The closest genera are found in the family
Dolichometopidae, of the order Corynexochida. Athabaskiella has a similar cephalon,
but a smaller pygidium with only four segments differentiated in the pleural regions

196 LOWER PALAEOZOIC BRACHIOPODS

and fewer in the axis. Bathyuriscus has smaller eyes which are not semicircular,
and a very narrow border to the pygidium. Dolichometopsis has a pygidium without
a border and with a terminal indentation, and Glossopleura has very faint glabellar
furrows, only eight thoracic segments, and differs in the position of the palpebral
lobes.

Monella perplexa gen, et sp. nov.

(PL ii, figs, 15-21)

1919 Ogygia sp, (pars); Lake in Greenly : 446.

Diagnosis. As for genus.

Description, Outline ovate, cephalon larger than pygidium. Cephalon semi-
circular, over twice as broad as long. Glabella clavate, between one and one-
quarter and two times as long as broad, convex transversely and slightly convex
longitudinally; glabellar lobes with independent convexity; three pairs of glabellar
furrows, one quarter the width of the glabella, shallow at their abaxial ends; posterior
pair (ip) at one quarter the length of the glabella forwards, inclined obliquely
backwards and becoming shallower and wider at their adaxial ends; 2p inclined
slightly backwards, situated just forward of half the length of the glabella; 3p
transverse or slightly inclined forwards, nearer 2p than the front of the glabella;
anterior margin of glabella convex forwards, lateral margins and the distinct axial
furrows evenly and gently convex adaxially, with well marked fossulae midway
between 3p and the front of the glabella. Occipital ring continues the convexity
of the glabella, one sixth its length (sag.); occipital furrow distinct. Fixigenae
smaller than the glabella or the librigenae. Palpebral lobes semicircular 9 posterior
extremities just anterior to the base of the glabella; anterior extremities between
the 2p and 3p furrows, separated from the axial furrows at each end by one-third
the width of the glabella. No preglabellar field. Anterior border furrow narrow,
anterior border with a vertically deflected margin. Facial sutures opisthoparian,
posterior branches diverging backwards to cut the posterior margin midway between
the axial furrow and the genal spine; anterior branches run directly forwards from
the eye to the margin. Librigenae convex, genal spine equal in length to the
glabella. Posterior border straight to the facial suture, then curving abaxially
from it evenly round to the genal spine; posterior and lateral furrows well defined,
posterior border half the width of the occipital ring (sag.)] the lateral border with
a vertical deflection, Doublure wide,

Hypostome and rostral plate unknown.

Thorax of eleven segments. Axis cylindrical, tapering slightly, equal
in width to the pleural regions, articulating half -rings equal in length (sag.) to the
axial rings; interpleural furrows curving slightly forwards towards the axial furrows.
Pleural regions flat adaxially, deflected ventrally in their abaxial regions; pleural
furrows transverse, dying out between fulcra and extremities; short, backwardly
directed pleural spines formed by the extremities of the pleurae being tapered,

AND TRILOBITES OF ANGLESEY 197

Anterior three (?) segments narrower {tr) than the rest and undeflected at their ends,
Pygidium semicircular, Axis convex, tapering to a point and extending onto
the border but not reaching the posterior margin, eight or possibly more axial rings
present. Pleural lobes gently convex with pleural furrows only. Border broad,
concave, doublure equal to it in width.

Type specimens (measurements in mm.)

Length Width

Holotype, Counterpart moulds of complete dorsal

carapace (Af. 827-8) . . . . — 13-7

Paratypes. Internal mould of cranidium (Af .834) . — —

Internal mould of cranidium (Af .836} . — —

Internal mould of pygidium (Af .839) . — —

Other figured specimen

External mould of incomplete dorsal cara-
pace (In. 58290) , — —

Type horizon and locality. Carmel Formation, sandstones in old quarry
(now filled in), 400 yds, nor th-north- west of Bryn Gollen Uchaf, Llanerchymedd.
N.G.R. 40508425. Other figured specimen from same horizon, on the escarpment
50 yds, north-east of Prys-o wain-bach, Carmel. N.G.R. 38878283.

Discussion. The generic position of 1VL perplexa has already been discussed,
and it is at present the only species known of the genus.

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19 8 LOWER PALAEOZOIC BRACHIOPODS

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AND TRILOBITES OF ANGLESEY 199

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PLATE i

Hesperonomiella cartnelensis sp. nov.

Carmel Formation, sandstones 50 yds, north-east of Prys-owain-bach, Carmel.

Fig, 1. Latex cast of ventral interior. BB. 30531. x 1*4.

Fig. 2. Latex cast of ventral interior. 66,30530. X 1-5.

Fig. 3. Internal mould of pedicle valve. BB. 30532a. x 1-5.

Fig, 4. Holotype, latex cast of dorsal interior. 66,30529. x z*$.

Fig. 5. Latex cast of ventral exterior, 66.30532b. X i'6.

Fig. 6, Latex cast of dorsal exterior. BB. 30533. X 1-3*

Monorthis typis gen. et sp. nov,

Treiorwerth Formation, sandstone 300 yds. south-east of Ffynnon-y-mab, Trefor.

Figs. 7, 8. Holotypc, internal mould and latex cast of brachial valve. BB. 30534, X3*4*

Fig. 9 Latex cast of dorsal interior. BB. 30535a. x 4*7.

Fig. 10. Latex cast of dorsal exterior, 66.30535b. X32.

Figs, ii, 12. Internal mould and latex cast of pedicle valve. BB. 30536a. x 3-2.

Fig. 13, Latex cast of ventral exterior. BB. 30536b, X 3*2.

Orthambonites[l) sp. (1)

Nantannog Formation, gritty shales 220 yds, west of Fferam-uchaf, Llanbabo,

Figs. 14, 17. Latex cast and mould of dorsal interior. Af , 1398. XfO, x 2*5.
Fig. 16, Latex cast of dorsal exterior, Af.1399. X4'0.

Orthambonites (?) sp. {2)

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig. 15. Latex cast of ventral interior. BB. 30510. x 3*3.

Figs. 18, ig. Internal mould and latex cast of pedicle valve, 66.30511a. X 2*9'

Fig. 20, Latex cast of ventral exterior, BB. 305 lib. x 2-9.

Lenorthis proava (Salter)

Carmel Formation, sandstones 50 yds, north-east of Prys-owain-bach, Carmel,
Fig. 21. Internal mould of brachial valve. 66. 30512. X2^ t

Bull. Br. Mus, nat. Hist. (GeoL) t-6, 4

PLATE 1

*****&

4fe

■■/■ f

1, TV ./ r

47; -fi-

•'tnl

tUW&L-

iV

m* 17 is

.--■

V

GEOL, 16, 4,

20

PLATE 2

Lenorthis proava (Salter)

Carmel Formation, sandstones 50 yds, north-east of Prys-owain-bach, Carmel.

Fig* i. Latex cast of dorsal interior. BB. 30512. x 2-1,

Fig. 2. Latex cast of dorsal interior. BB, 30515a, xa*2,

Fig. 4. Latex cast of dorsal exterior, BB . 30515b, X 2*1.

Fig, 5, Latex cast of ventral exterior. BB. 30513b. x 2-0.

Fig, 7, Latex cast of ventral interior, BB. 30514, X2'8.

Fig. 8, Latex cast of ventral interior. BB. 30513a. X2*2.

Carmel Formation, sandstones 130 yds. north-west of Ty-hen, Treiorwerth,
Figs, 3, 6. Internal mould and latex cast of pedicle valve, Af,i337. X2*4.

Cyrtonotella sp. {1)

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Figs. g, 13. Internal mould and latex cast of brachial valve, BB. 30521a. X50.
Fig, 10, Latex cast of dorsal exterior. BB. 30521b. x 5-0,

Lenorthis sp.

Bod Deinioi Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,

Bod Deinioi,

Fig. 1 1 • Latex cast of dorsal interior. BB . 30602 , x 2 - 1 ,
Fig. 12, Latex cast of ventral interior. BB. 30601a. X27.

Cyrtonotella sp. (2)

Garn Formation, limestone blocks in breccia beds, Porth-Padrig, Mynachdy.

Fig. 14. Exterior of brachial valve, RB. 30523. X2'4,
Fig. 15. Latex cast of dorsal exterior. BB. 30524, X2*3.
Fig, 16. Exterior of pedicle valve. BB. 30522. X32.

Pleurorthis costatus sp. nov.

Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.

Figs, 17, 18. Holotype, internal mould and latex cast of brachial valve. BB, 30516. x 2*2
Fig. 19. Latex cast of dorsal exterior. BB. 30555b. X3'3-

Bull. Br. Mus. nat. Hist, (Geol.) i6, 4

PLATE 2

PLATE 3

Pleurorthis costatus sp. nov,

Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.

Figs. 1,2. Internal mould and latex cast of pedicle valve. 66*30518. X2-2.
Figs. 3, 4. Internal mould and latex cast of pedicle valve. BB. 30517a, X23.
Fig. 6, Latex cast of ventral exterior, BB. 30517b. X 2-3.

Nicolella hutnilis Williams

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig. 5. Latex cast of dorsal interior. BB. 30519a, X3*i.

Fig. 7. Latex cast of dorsal exterior. BB. 30519b. x 3*1,

Fig. 8. Latex cast of dorsal exterior, BB. 30520b. X3'3.

Fig. g. Internal mould of brachial valve, BB ,30520a. X31.

Panderina lamellosa sp. nov,

Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.

Fig. 10, Latex cast of dorsal interior. BB. 30528a, X4-2,

Figs. 1 1 , 12. Holotype, internal mould and latex cast of brachial valve. BB . 30525a, x 4'2

Fig. 13. Latex cast of dorsal exterior, BB. 30528b. X3*o.

Fig. 14, Holotype, latex cast of dorsal exterior. BB. 30525b, Xfo,

Figs. 15, 16. Latex cast and internal mould of pedicle valve. BB. 30526a. X5'5-

Fig, 17. Latex cast of ventral exterior. BB, 30527b. X32.

Fig. 18. Latex cast of ventral interior. BB. 30527a. X4*3.

Ptychopleurella sp. (i)

Nantannos Formation, fine sandstones and shales 190 yds. south-east of Fferam-uchaf farm,

Llanbabo.

Fig. 19. Latex cast of ventral interior. BB. 30537a, X4'i.

Fig. 20. External mould of pedicle valve, 66,30537!}. X46.

Figs. 21, 22. Internal mould and latex cast of brachial valve. BB, 30538a. X45.

Fig. 23. Latex cast of dorsal exterior. BB. 30538b, X4'5.

Bull. Br. Mhs. not. Hist. (Geol.) 16, 4

PLATE 3

PLATE 4
Ptychopleurella sp» (2)

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig. xi Internal mould of brachial valve. BB. 30539a, x 3*5.

Figs, 2, 3. Internal mould and latex cast of pedicle valve. BB. 30540a. X4'i,

Fig, 5, Fragment of external mould of pedicle valve. BB. 30540b* x 4*0.

Dolerorthis cf. tenuicostata Williams

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig. 4, Latex cast of ventral exterior. BB, 30541b, X 3*1.

Figs. 6, 7. Internal mould latex cast of pedicle valve. BB. 30541a, x 2*6> X3'i.

Plaesiotnys cf . robusta (Bancroft)

Crewyn Formation, grits 420 yds, west-south-west of Ysgubor-gader, Mynachdy,

Fig. 8. Latex cast of dorsal exterior. BB. 30543b. X 2*0.
Fig. 9, Latex cast of dorsal interior. BB. 30543a. X2*2.
Fig. 10. Internal mould of pedicle valve, BB, 30544a. x 17.
Fig. 11. External mould of pedicle valve, BB. 30545b, x 1*7.
Fig, 12. Internal mould of pedicle valve. BB. 30545a. X17.

Plaesiotnys (Dinorthis) sg>.

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Figs. 13, 15. Internal mould and latex cast of pedicle valve. BB ,30542a. X2*6 #
Fig. 14. Latex cast of ventral exterior. BB. 30542b. X 3-2.

Plectorthis (?) sp.

Nantannog Formation, gritty shales 250 yds. west-south-west of Fferam-uchaf, Llanbabo.

Fig. 16. Internal mould of pedicle valve. Af . 1377- X 4*0.
Fig, 19. Internal mould of pedicle valve, Af . 1462. x 2-9.

Platystrophia precedens $najor Williams

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig, 17, Latex cast of ventral interior. BB. 30546a, X2'2.
Fig. 18. Latex cast of ventral exterior. BB. 30546b. x 2-0.

BulL Br, Mus. nat. Hist. (Geol) i6 f 4

PLATE 4

13

PLATE 5

Skenidioides sp. (i)

Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefon

Fig, 1. Internal mould of pedicle valve. 66,30547, X 77.
Fig, 2. Internal mould of brachial valve. 66.30548, xfri.

Skenidioides sp* (2)

Nantannog Formation, fine sandstones and shales 190 yds* south-east of Fferam-uchaf, Llanbabo,

Fig. 3, Internal mould of brachial valve. 66. 30549a, x 6-5.
Fig. 4, Internal mould of pedicle valve. 66.30550a. X76.
Fig. 5, External mould of brachial valve. 66.30549b. x 65.

Paurorthis{?) sp*

6od Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,

Bod DeinioL

Figs, 6, 7. Internal mould and latex cast of pedicle valve. 66,30603a. x 2*5.
Fig. 8. Latex cast of ventral interior. B6. 30604a. X 25.
Fig. 9* Latex cast of ventral exterior. 66,30604b. x 2*5,

Dalmanella{?) sp,

Crewyn Formation, grits 426 yds. west-south-west of Ysgubor-gader, Mynachdy.

Fig, 10. Latex cast of brachial exterior. 6B. 30568* X2-5.
Fig. 11, Latex cast of ventral exterior. 66,30569- X27,

Onniella(?) sp*

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig, 12. Internal mould of pedicle valve, BB. 30570a. X37.
Fig. 13. Latex cast of ventral exterior, 66.305705. X3*g.
Fig. 14, Internal mould of brachial valve. BB. 30571, X4*g.

Horderleyelta{}) sp.

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
Fig. 15, Internal mould of pedicle valve. 66. 30572. x 2*9.

Harhnes sella sp.

Garn Formation, limestone block in breccia bed, 300 yds. east-south-east of the summit

of Mynydd-y-garn.

Fig. 16, Exterior of pedicle valve, Af . 1492. x 3*0.

Salopia salteri gracilis Williams

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Figs. 17, 18. Internal mould and latex cast of brachial valve. 66,30573. X3*9* Xfi-

Rhyncharthis rotundus gen, et sp. nov.
Treiorwerth Formation, sandstones 300 yds, south-east of Ffynnon-y-mab, Trefor.
Figs. 19, 20. Holotype, internal mould and latex cast of brachial valve, 66,30551,

X2*9, X3*5-
Figs. 21, 22, Internal mould and latex cast of brachial valve. BB. 30552. X3*4, X37.
Figs. 23, 25. Internal mould and latex cast of pedicle valve, 66. 30556. x 3*4, x 3 a i.
Fig, 24. Internal mould of pedicle valve. 66*30554. X32.
Fig. 26, Internal mould of brachial valve. 66 . 30553. x 3-0.

Bull. Br. Mus. not. Hist, (Geol.) 16, 4

PLATE 5

■It *&£*?. /.

mm:

—^ 10

w*3V

p'

/* - 1

15

, 1

17

PLATE 6

Tritoechia sp.

Treiorwerth Formation, sandstones 300 yds south-east uf Ffynnon-y-mab, Trefor.

Fig. 1. Latex cast of ventral interior. BR. 30557a. X2*2.

Fig. 2. Latex cast of ventral interior, and exterior of interarea, posterior view. BB, 30557a.

X2'2.

Figs. 3, 5. Latex cast of ventral exterior, posterior and ventral views. BB. 30557b. x 20.

Clitambonite${l) sp,

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo,
Fig. 4. Latex cast of dorsal exterior. BB. 30558. x 1-4.

Ilmarinia sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo,
Figs* 6, 7, Internal mould of pedicle valve, ventral and posterior views. BB . 30559a. x 31,

Apomatetla{i) sp.

Bod Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,

Bod Deiniol.

Fig. 8. Latex cast of ventral interior. BB, 30605a. X30,
Fig. g. Latex cast of ventral exterior, posterior view. BB. 30605b. X3-o.
Fig. 10. Latex cast of ventral exterior, posterior view. BB. 30606b, X 2*3.
Fig, 11. Latex cast of ventral interior. BB. 30606a- X2*4,

Antigortambonites pyramidalis sp. nov.

Treiorwerth Formation, sandstones 300 yds, south-east of Ffynnon-y-mab, Trefor,

Fig, 12. Holotype, latex cast of dorsal interior. BB. 30561a. X4*i.

Fig. 13, Holotype, latex cast of dorsal exterior. BB. 30561b. X4*4-

Figs. 14, 15, Latex cast and internal mould of brachial valve. BB. 30563, X 2*8, x 2*2.

Figs, 16, 17. Internal mould and latex cast of pedicle valve. BB. 30564. X33, X35*

Fig* 18, Internal mould of pedicle valve. 86.30562. X4U

Kullervo aff. pander i (Opik)

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Figs. 19, 20. Internal mould and latex cast of brachial valve. BB. 30567a. X4U
Fig. 21. Latex cast of dorsal exterior. BB. 30567b. Xfo.
Fig. 22. Internal mould of pedicle valve. BB. 30565. X25.

Bull. Br. Mus. nat. Hist. (Geol.) 16, 4

PLATE 6

*^j^V

iV --V$#!

MP

1 i b r

fcT*^ ^ i Ji u fa-

13

PLATE 7
Kullervo aff. panderi (Opik)

Lianbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo,

Fig. i. Latex cast of ventral interior. BB. 30566. X5 i i.

Estlandia{T) sp.

Berw-uchaf Grits, 90 yds* north of Bwlch-gwyn farm, Holland Arms.

Fig, 2. Latex cast of ventral interior. Af .238. X5-2.

Fig. 3. Latex cast of ventral exterior, Af .225. x 5-2.

Figs, 4, 9. Internal mould and latex cast of brachial valve, AL214, X5*o,

Figs, 6, 7. Internal mould and latex cast of brachial valve. BB. 30560a. X77.

Fig. 8. Latex cast of dorsal exterior. BB. 30560b. x 77.

Ciitambonitid gen, indet.

Bod Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,

Bod Deiniol.

Fig. 5. Latex cast of dorsal interior. BB, 30608a. X2-0.

Figs, io, 11, Latex cast of ventral interior, dorsal and anterior views, 66.30607. X3'0,

Ahtiella concava sp. nov.

Bod Deiniol Formation, grits in temporary excavation 50 yds, north of Ty-bach cottage,

Bod DeinioL

Fig. 13. Latex cast of dorsal interior. BB* 30616a. x 2*4.

Fig. 12. Latex cast of dorsal interior, cardinalia. BB. 30616a, x 3-0*

Fig, 14, Holotype, latex cast of ventral interior. BB. 30615a. x 1*9,

Figs. 15, 18. Holotype, latex cast of ventral exterior, ventral and posterior views. BB.

30615b. xi*9*

Figs, i6, 19, Latex cast of dorsal interior, ventral and oblique posterior views, BB.
30618a. x 2-4.

Fig. 22. Latex cast of dorsal exterior* BB. 30616b, X2-3.

Fig, 17, Latex cast of dorsal interior, BB. 30617a. X2-2.

Fig. 20. Latex cast of ventral interior, BB. 30619a. X2*3*

Fig. 21. Latex cast of ventral exterior, BB. 30619b, X2*2.

Bull. Br. Mus. nat. Hist. (Geol.) 16, 4

PLATE 7

%

"1' '

VrfS

p ■

?»»

PLATE 8
Ahtiella quadrat a sp, no v.

Torllwyn Formation, sandstones 50 ft. above the base of the succession, on
the north side of the faulted syncline, 45 yds. north of Ogof Gynfor, Llanbadrig.

Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig,
Fig,
Fig.

2

3

5

6

7
8

Latex cast of dorsal interior.
Latex cast of dorsal exterior.
Latex cast of ventral interior.
Latex cast of ventral exterior.
Latex cast of dorsal interior.
Latex cast of dorsal exterior.

BB ,30613a.
BB. 30613b,

BB. 3061 1 a.

BB. 3061 lb.
BB- 30612a,
BB. 30612b.
BB. 30614a.

x 2*2.

X 20,
X 2-0.

X 20.

X2*2,

X I -9,

X2-3.

Latex cast of dorsal interior.

Holotype, latex cast of ventral interior. BB, 30609.

Latex cast of ventral interior. BB, 30610. X2*o,

X 2-G.

Reinver sella monensis gen. et sp. nov.

Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, T re for.

Figs, io, 1 1 . Holotype, internal mould and latex cast of brachial valve. BB . 30574a, X 1 -6.

Fig. 12. Holotype latex cast of dorsal exterior. BB. 305 74b. X 1*6,

Figs. 13, 14. Internal mould and latex cast of pedicle valve. BB. 30575a. x 1-9, X 1-7.

Fig, 15. Latex cast of ventral exterior. BB, 30575b. X2-2.

Fig. 16. Internal mould of brachial valve, BB. 30576a. X2*i,

Fig + 17, Latex cast of dorsal exterior. BB. 30576b. X2-2.

Bull. Br. Mus. not. Hist. (Geol.) 16, 4

PLATE 8

PLATE 9
Pataeo$trophomena{}) sp.
Gam Formation, limestone blocks in breccia beds at Porth Padrig, Mynachdy,
Fig. i. Exterior of pedicle(?) valve. BB. 30581a, X2-2.

Sertcoidea abdita Williams

Tandinas Shales, by the shore too yds, west of the pier, Careg-onen,

Fig, 3. Internal mould of brachial valve with shell material adhering. BB. 30588. xy-i.
Fig. 6. Interior of brachial valve. 68,30587, X 7*3.

Palaeostrophomena sp.

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Fig. 2. Latex cast of ventral interior. BB. 30579a. X3-2.

Figs. 4, 5. Internal mould and latex cast of brachial valve. 86*30580. X3*o #

Leptestiina derfetensis (Jones)

Tandinas Shales, by the track 50 yds. west of Tandinas Quarry, Careg-onen.

Figs. 7, 8. Internal mould and latex cast of pedicle valve. 66*30577. X40.
Fig. 9. Latex cast of dorsal interior. 66,30578. X4-4.

Bilobia aff. tnusca (Opik)

Llanbabo Formation, Llanbabo Church Grits, 180 yds. east of Fferam-uchaf, Llanbabo.

Figs. 10, 11. Internal mould of pedicle valve, ventral and posterior views. 66.30582.
X3'O f X4-0.
Fig. 12, Latex cast of ventral interior, BB. 30582. x 3*0.
Fig, 13. Internal mould of part of brachial valve, BB. 30583. X33.

Eoplectodonta lenis Williams

Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.

Figs. 14, 15. Internal mould and latex cast of pedicle valve. 66. 30584a. X4-o, X37.
Fig, 16. Internal mould of brachial valve. 6B. 30585a. X4-1.
Fig. 17. Latex cast of dorsal exterior. BB ,30585b. Xfi.
Fig. 18. Latex cast of dorsal exterior. BB. 30586, X4*5-

Bull. Br. Mu$. not. Hist. (Geol.) 16, 4

PLATE 9

8

'■"■■>«!»■

^ t >

13

GEOL. 16, 4.

21

PLATE 10

Ptychoglyptus sp.

Gam Formation, limestone blocks in breccia beds at Forth Padrig, Mynachdy.

Fig. i. Exterior of brachial valve. 63,30589. X4-4.
Fig, 2, Exterior of pedicle valve, 66.30590, X 4*4.

Leptaena sp.

Llanbabo Formation, Llanbabo Church Grits, 180 yds. east of Fferam-uchaf, Llanbabo,

Fig, 3. Latex cast of dorsal interior, 66,30592. X3*2.

Figs. 4, 5. Internal mould and latex cast of pedicle valve. 66,30591. X2'2.

Fig. 6. Internal mould of brachial valve. 66,30593. X4*5.

Dactylogonia sp.

Nantannog Formation, fine sandstones and shales 190 yds. south-east of Fferam-uchaf farm,

Llanbabo.

Figs. 7, 8. Latex cast and internal mould of brachial valve. 66.30596a. X5-6, X4*6.

Kiaerornena(?) sp.

Gam Formation, limestone blocks in breccia beds, Porth Padrig, Mynachdy.

Fig. 9. Exterior of brachial (?) valve. 66.30595, X 2-9.
Fig. io. Exterior of pedicle (?) valve. 66.30594. X3"i.

Rectotrophia globular is gen. et sp, nov.

Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.

Figs, ii, 12. Internal mould of brachial valve, dorsal and lateral views. Af.1436. X36.

Fig. 13. Latex cast of internal mould of brachial valve. Af.1436. X47.

Figs. 14, 15. Holotype, internal mould of pedicle valve, ventral and lateral views. Af . 1436.

X3'i-
Fig. 16, Holotype, latex cast of ventral interior. Af.1436. X4 i i.

Fig, 17, Internal mould of brachial valve. Af.1442. X4\3,

Order uncertain

Torllwyn Formation, sandstones 50 ft. above the base of the succession, on the
north side of the faulted syncline, 45 yds. north of Ogof Gynfor, Llanbadrig.

Figs. 18, 19. Internal mould of brachial valve, posterior and dorsal views, 6B. 55791a,
X i*5-
Fig. 21, Latex cast of brachial valve. 66.55791a. x 2*2,

Figs, 20, 22, Internal mould and latex cast of pedicle valve. 66,55792a. x i-8.
Fig. 23. Latex cast of dorsal exterior, 66.55791b. X 2*1.
Fig + 24, Latex cast of ventral exterior. 66,55792b. X 1*5,

Bull. Br. Mus. nat. Hist. (Geol.) 16, 4

PLATE 10

II

12

24

PLATE ii

Porambonites (s.s,) sp.

Treionverth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor,

Figs, r, 2. Internal mould and latex cast of pedicle valve, BB. 30598a. x 17,

Fig, 3, Internal mould of brachial valve. BB. 30599a, x 1-5.

Figs. 4, 8, Latex cast of dorsal interior, dorsal and anterior views. BB, 30599a. X 1-3.

Figs. 5, 6. Latex cast and internal mould of brachial valve. BB. 30600, X2«4, X2'2.

Camerella sp.

Garn Formation, limestone blocks in breccia beds at Forth Padrig, Mynachdy.

Figs. 7, 9, 10, 11. Complete shell, anterior dorsal, lateral and ventral views* 66.30597,
X 4-8.

Metacatnerella ci balcletchiensis (Davidson)

Garn Formation, limestone blocks in breccia beds at Porth Padrig, Mynachdy.

Figs. 12, 13, 14, Complete shell, dorsal, lateral and anterior views, Af .1590- X 1-5, X 1*5,

X2-0.

Marietta perplexa gen. et sp. nov.

Carmel Formation, sandstone 400 yds. north of Bryn Gollen Uchaf, Llanerchymedd,

Figs. 16, 19. Holotype, internal mould of entire exoskeleton, dorsal and anterior views.
Af.827, X3'a

Fig, 15. Internal mould of cranidium. Af.836. X2-4.
Fig. 17. Internal mould of cranidium. Af .834. < 2-5.
Fig, 20, Internal mould of pygidium, Af.839. X3'i.

Carmel Formation, sandstones 50 yds. north-east of Prys-owain-bach, Carmel,

Figs. i8 f 21. Latex casts of external mould of cranidium and one librigena, and incomplete
thorax and pygidium. In. 58290. x 1-0,

Bull. Br. Mus. nat. Hist. (Geol.) 16, 4

PLATE 11

-ft Ji /

13

Pi

PLATE 12
Ogygiocaris selwynii (Salter)

Carniel Formation, sandstones 400 yds. north of Bryn Gollen Uchaf, Llanerchymedd.

Fig. i. Internal mould of cranidium, AL823. xri,

Fig. 2 t Internal mould of cranidium, Af ,842, x i-o.

Fig. 5. Internal mould of pygidium. Af.820. x i-o.

Fig. 6, Internal mould of pygidium, Af .821. xi'O,

Protobronteus greenlyi sp. nov.

Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.

Fig. 3* Incomplete cranidium. In. 58292. X2"3.

Fig. 4. Internal mould of librigena. In. 58293a. xi-i.

Fig. 7, Holotype, incomplete cranidium. In. 58291. xiu

IUaenus sp.
Garn Formation, limestone blocks in breccia beds, Porth Padrig, Mynachdy.

Figs. 8, n f 15. Internal mould of cranidium, anterior, dorsal and oblique views. In. 58294.

X3*7-

Figs. 9, 10. Internal mould of pygidium, with doublure partially revealed, lateral and dorsal

views. In. 58295. xi'4.

Figs, 12, 13. Internal mould of pygidium, with some skeletal material adhering, dorsal
and lateral views. In , 58296. xri.

Stenopareia cf. linnarssoni (Holm)
Garn Formation, limestone blocks in breccia beds, Porth Padrig, Mynachdy.

Fig. 14. Rostral plate. In. 58300. X 2-2.

Fig. 16, Internal mould of librigena, 1^58299. X20.

Fig. 17. Internal mould of pygidium, showing the doublure. In, 58302. X2-2,

Figs. 18, 19, Internal mould of incomplete pygidium, with skeletal material adhering,
dorsal and lateral views. In . 58301 , xri.

Figs, 20, at. Internal mould of cranidium, anterior and dorsal views. In. 58297, X2-1,
X3-o.

Figs. 22, 23, Internal mould of cranidium, with some skeletal material adhering, anterior
and dorsal views. In . 58298, x 2* 1 .

Bull. Br. Mus. nat. Hist. (Geol.) 16, 4

PLATE 12

PLATE 13
Setenoharpesft) sp«

Gam Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy,

Figs. i, 5, 6, Cranidium, dorsal, lateral and anterior views. 10.58303. x 1*6*
Fig. 2, Cranidium, detail of fixigena and brim, In. 58303, X2^,

Bergamia(?) sp.

Shales, D r bifidus zone, quarry 100 yds. north of Gwredog-uchaf, Rhodogeidio,

Fig. 3, External mould of complete dorsal carapace. In ,58305b, x8-o.

Fig. 4. Internal mould of dorsal carapace lacking the librigenae. In. 58306. X 1-3.

Figs, g, 13. External and internal moulds of cranidium and pygidium. In. 58304. X44,

Atnpyx sp. (1)
Carmel Formation, sandstones on scarp west of Bryn Go lien Uchaf, Llanerchymedd.
Fig. 8. Internal mould of cranidium. Af.824, X3"8.

Atnpyx sp. (2)

Tandinas Shales, by the track 50 yds. west of Tandinas Quarry, Careg-onen.

Fig, 7, External mould of cranidium. In. 58308, X32.

Fig. 10. Internal mould of thoracic segments and pygidium. Af .3653. X 2-0.

Tandinas Shales, on the shore by the power house, 100 yds. west of the pier.

Fig. 11, Internal mould of cranidium. In. 58307a, X17.

Fig. 12. Latex cast of external mould of pygidium. In. 58309. x 3-0,

Ceraurinella sp.

Gam Formation, limestone blocks in breccia beds, Porth Padrig, Mynachdy.

Fig. 14, Incomplete cranidium. In, 58312, X2-2.

Fig. 15, Glabella. ^,58311. X3'2,

Fig, 16, Glabella. 1^58310. X32.

Fig. 17. Hypostome, In. 58315, X24.

Fig. 18. Latex cast of external mould of thoracic segment. In. 583 16. X 2-1.

Fig. 19. Thoracic segment. In. 58317, X2-2.

Fig. 20. Pygidium. In. 58318. X40,

Fig, 21, Hypostome. In, 58313. xr6.

Fig. 22, Hypostome, 1^,58314, X32-

Bull. Br. Mus. nai. Hist. (Geol.) 16, 4

PLATE 13

19

PLATE 14
Sphaerexochus sp.

Tandinas Shales, on the shore by the power house, 100 yds, west of the pier, Careg-onen.

Figs, i, 2. Cranidium, dorsal and oblique lateral views. 111*58319. X3-2,

Ptiomerops sp*

Gam Formation, limestone blocks in breccia beds, Forth Padrig, Mynaehdy.

Fig. 3, Hypostome. 111.58321. xr8.

Fig, 4. Incomplete cranidium. In, 58320. x 2-2,

Fig, 6. Incomplete pygidium. In. 58322. Xi-3-

Fig. 7, Latex cast of external mould of pygidium. In ,58323b, X2u

Placoparia sp.

Shales on the shore at Porth-y-gwichiaid, 80 yds, north of the streamlet.
Fig, 5. Complete dorsal carapace, lacking the librigenae. Af . 13 19, x 2*6.

Calymenid (s.l.) sp.

Garn Formation, limestone blocks in breccia beds, Porth Padrig, Mynaehdy*

Fig. 8. Hypostome. In. 58324. X3'i,

Figs. 9, 12, 13. Pygidium, dorsal, posterior and oblique lateral views. In. 58325. X2«8,

Neseuretus rnortensts (Shirley)

Carmel Formation, sandstones 120 yds. north-west of Chwaen-bach, Llanerchymedd.

Fig. 11. Internal mould of pygidium. In. 58327. x 1*7.

Carmel Formation, sandstones 440 yds. north of Ty-hen, Treiorwerth.
Fig. 16. Internal mould of pygidium. In, 58326a. X 17.

Arnphilichas sp, (1)

Garn Formation, limestone blocks in breccia beds, Porth Padrig, Mynaehdy.

Figs. 10, 14, 17, Cranidium, anterior, lateral and dorsal views. In. 583 28. X2*o,
Fig. 15. Hypostome* In. 58329. X33.

Arnphilichas sp. (2)
Tandinas Shales, by the track 50 yds. west of Tandinas Quarry, Careg-onen.
Figs. 18, 19. External mould and latex cast of cranidium. Af ,3000. x 2-1.

Bull. Br. Mus. nctt. Hist. (Geol.) i6, 4

PLATE 14

16

;'*-

W

19

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ft

f 9

4fy

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